Modern network communication systems are generally of either the wired or wireless type. Wireless networks enable communications between two or more nodes using any number of different techniques. Wireless networks rely on different technologies to transport information from one place to another. Several examples include, for example, networks based on radio frequency (RF), infrared, optical, etc. Wired networks may be constructed using any of several existing technologies, including metallic twisted pair, coaxial, optical fiber, etc.
Communications in a wired network typically occurs between two communication transceivers over a length of cable making up the communications channel. Each communications transceiver comprises a transmitter and receiver components. A fault along the communication channel causes a disruption in communications between the transceivers. Typically, it is desirable to be able to determine when a fault occurs in the channel. Once a fault is detected, it is desirable to determine information about the fault, such as its location along the channel.
Even in the absence of a fault is often desirable to be able to obtain information about the communications channel, i.e. to perform cable diagnostics on the channel. Examples of the type of information it would be useful to have include (1) identifying cable faults such as an open cable, shorted cable, unmatched load, irregularities of the impedance along the cable, (2) determining the length of the cable, etc.
There are many instances where it is desirable to be to determine the length of the cable so as to identify faults or discontinuities along its length. In accordance with a management scheme, baseline measurements are taken initially and then checked periodically over time. Any deviations from the baseline that are detected may be logged and reported to higher layers.
In another application, customers can be charged for cable and installation by the total length purchased or installed. A cable diagnostics mechanism is useful in this situation to measure length of cable after installation without the requirement to measure it beforehand.
Further, as the cost of Gigabit Ethernet (GE) equipment decreases, it is likely to be installed in more and more networks. Older legacy networks that use Cat 3 or 4 wiring are being upgraded with Gigabit Ethernet adapters, switches, routers, etc. Many of these networks will not upgrade the cable and will retain their old cable plant thus creating potential transmission problems due to the use of cable designed for slower networks. Cable diagnostic tools can potentially help identify problems.
The ability to gather diagnostics on the cable is particularly useful in the case where physical access to the cable is extremely difficult or impossible. Further, it is desirable to have the cable diagnostics capabilities built into the communications transceiver without requiring significant modification to existing transceivers.
Thus, there is a need for a mechanism for a cable diagnostic system that is capable of determining information, including cable length, cable faults (including their locations), about a communications channel comprising a metallic cable that can be incorporated into a conventional communications transceiver without requiring extensive modifications to the transceiver.